The present invention relates to computer systems and more specifically to microprogrammable microprocessor systems.
Modern computer systems typically include a microprogrammable microprocessor (MMP), e.g. NCR 32000, and a real memory connected together by a processor memory bus. The MMP fetches instructions and data from real memory and executes those instructions and manipulates data. The real memory is typically made of random access memory (RAM). This RAM stores microinstructions.
The MMP is also connected to an instruction storage unit (ISU) which is a microinstruction memory made of read only memory (ROM), through an instruction storage unit bus (ISUB).